AW TER ALLOCATION IN A CHANGING CLIMATE: … · AW TER ALLOCATION IN A CHANGING CLIMATE:...

WATER ALLOCATION IN A CHANGING CLIMATE:INSTITUTIONS AND ADAPTATION

KATHLEEN A. MILLER and STEVEN L. RHODESEnvironmental and Societal Impacts Group, National Center for Atmospheric Research,

P.O. Box 3000, Boulder, CO 80307-3000, U.S.A.

LAWRENCE J. MACDONNELLSustainability Initiatives, 2260 Baseline Road, Suite 101, Boulder, CO 80302, U.S.A.

Abstract. Global warming may profoundly affect temporal and spatial distributions of surface wateravailability. While climate modelers cannot yet predict regional hydrologic changes with confidence,it is appropriate to begin examining the likely effects of water allocation institutions on society’sadaptability to prospective climate change. Such institutions include basic systems of water law,specific statutes, systems of administration and enforcement, and social norms regarding acceptablewater-use practices. Both climate and the changing nature of demands on the resource have affectedthe development and evolution of water allocation institutions in the United States. Water laws andadministrative arrangements, for example, have adapted to changing circumstances, but the processof adaptation can be costly and subject to conflict. Analysis of past and ongoing institutional changeis used to identify factors that may have a bearing on the costliness of adaptation to the uncertainimpacts of global warming on water availability and water demands. Several elements are identifiedthat should be incorporated in the design of future water policies to reduce the potential for disputesand resource degradation that might otherwise result if climate change alters regional hydrology.

1. Introduction

Global climate modeling experiments suggest that anthropogenic emissions ofcarbon dioxide and other trace gases are likely to result in global warming overthe course of the next century (Houghton et al., 1990). While climate modelingefforts cannot yet provide consistent and reliable forecasts of the timing and natureof regional climatic and hydrologic changes, the available evidence suggests thatglobal warming may have profound impacts on water resource availability. Hydro-logic analyses of plausible climate change scenarios indicate possible substantialreductions in streamflows in some areas, increased flood frequencies in other areas,and changes in the seasonal pattern of flows, with reduced summer flows likelyin many mountainous and northern river basins (Schaake, 1990; Waggoner, 1990;Duell, 1992).

Researchers have given considerable attention to the possible physical effectsof climate change on hydrologic regimes as well as to the assessment of strategiesto manage those impacts (NRC, 1977; Beran, 1986; WMO, 1989; Rango and VanKatwijk, 1990; Tegart et al., 1990; Waggoner, 1990; Chang et al., 1992). They havegiven less attention to the role of institutional factors in determining the efficacy ofalternative response strategies. These factors include the existing configuration of

Climatic Change 35: 157–177, 1997.c 1997 Kluwer Academic Publishers. Printed in the Netherlands.

158 KATHLEEN A. MILLER ET AL.

rights, responsibilities and expectations regarding water resources as well as fac-tors determining the relative ease or difficulty of altering the distribution of rightsamong competing users of the resource. Rogers (1994) argues that political andeconomic uncertainties are often far more important than hydrologic uncertain-ties for public water supply decisions, and that the hydrologic impacts of climatechange may present fewer difficulties for water planning than the growing inter-dependence among water users. He further notes that the environmental aspects ofhydrologic change may be considerably more problematic than traditional watersupply concerns. He urges continued “research on the nexus of climate change,water resources, and socioeconomic adaptation; not solely on the hydrology butalso upon other parts of the socioeconomic system and the aquatic ecosystem”(Rogers, 1994, p. 204). This paper takes up that challenge by examining the inter-actions between institutional factors and socioeconomic adaptations to the possiblehydrologic impacts of climate change.

Water is a multifaceted resource, and competing claimants to the resource valueits various dimensions differently. Valuations of the quantity, reliability, quality,location and timing dimensions of the resource differ across competing user groups,and these relative values change over time. In addition, the degree to which thereis direct competition among water users varies with the type of use and across thevarious dimensions of the resource. Thus, decisions about water use can involve ahost of competing claimants whose desires may increasingly come into conflict ifclimate change alters the location and timing of water availability. The increasedpotential for conflict warrants closer examination of the ways in which institutionsmay channel such competition to either facilitate or hinder adjustment to the effectsof climate change.

Demographic change, increased environmental awareness and changing pat-terns of water demand have already created pressures for changes in the allocationof water among competing uses. The resulting adjustment process has entailed con-flicts as well as cooperative solutions. The institutions governing water allocationsometimes appear to impede effective responses to changing circumstances (OTA,1993), but those institutions have also evolved in response to pressures exerted bycompeting resource users. In some cases, climate-related uncertainties have con-tributed to costly disputes over water resources, as occurred in the recent battle overproposed groundwater exports from Colorado’s San Luis Valley. That dispute wasfueled by irrigators’ fears that the difficulty of proving impacts in the presence ofclimatic variability would impair their ability to secure compensation for damages.In other instances, climatic events such as California’s recent multi-year droughthave catalyzed significant institutional change (Howitt et al., 1992). The record ofsuch cases can provide a glimpse of issues that are likely to arise as water resourcesare increasingly subject to the effects of global environmental change.

If climate change leads to greater aridity in some regions, will that lead toincreasing conflicts over water or will it inspire creative institutional approachesto resolve such disputes? Is any particular system of water law inherently better

WATER ALLOCATION IN A CHANGING CLIMATE 159

suited to resolving conflicts in the presence of uncertainty regarding both relativevaluations and the future state of the resource itself? Are there reasons to takeactions now to allay the future costs of adapting to climate change? To address suchquestions, it is helpful to consider the nature of the relationship between institutionsand individual decisions regarding the use of natural resources. Institutions can bedefined as:

the humanly devised constraints that structure human interaction. They aremade up of formal constraints (e.g., rules, laws, constitutions), informal con-straints (e.g., norms of behavior, conventions, self-imposed codes of conduct),and their enforcement characteristics. Together they define the incentive struc-ture of societies and specifically economies (North, 1994, p. 360).

Recent work on the economics of property rights and related institutions sug-gests that institutions shape current decisions regarding the use of resources aswell as the path of adjustment to changing circumstances (Ostrom, 1990; Brom-ley, 1991). These multiple effects arise because institutions influence the costs ofengaging in transactions through markets and within organizations, as well as thecosts of engaging in political action (Alchian, 1965; Bromley, 1982; Barzel, 1989;North, 1994). Transaction costs, defined as: “the costs of specifying what is beingexchanged and of enforcing the consequent agreements” (North, 1994, p. 361),are thus molded by institutional choices. In turn, transaction costs influence thecourse of institutional change by affecting political exchanges and private contracts(Cheung, 1970; Eggertsson, 1990).

Use of the term ‘institutions’ in this literature differs from its use in com-mon parlance. Institutions establish the ground rules within which individualsmake decisions and organizations are created and operate (Bromley, 1982; North,1994). Organizations, such as federal and state water agencies, water suppliers andwater user associations, carry out their activities within the set of incentives andconstraints provided by current institutions. In the context of this analysis, the rel-evant institutions include basic systems of water law, specific statutes, systems ofadministration and enforcement, and changing social norms regarding acceptablewater-use practices.

To set the stage for our analysis, we begin with an overview of the evolutionof water allocation institutions in the eastern and western portions of the UnitedStates. We highlight the importance of differences in climate and changing humandemands. The two distinct traditions of water law in this country provide an oppor-tunity to examine how differences in climate and historical patterns of water usecontinue to shape institutional responses to changing values and demands. Wethen discuss the potential hydrologic impacts of climate change and the uncer-tainties associated with those impacts. The evidence indicates that we must nowaccommodate competing water demands within the context of increasing hydro-logic uncertainty. This additional source of uncertainty suggests factors that watermanagers and the public should consider in water policy decisions over the coming


decades. In the conclusion of this paper, we identify such factors and make recom-mendations regarding their incorporation in the design of future water policies.

2. Development and Evolution of U.S. Water Institutions

2.1. THE RIPARIAN AND PRIOR APPROPRIATION SYSTEMS OF WATER LAW

Courts and legislatures historically constructed American water law on two distinctdoctrines, riparian rights and prior appropriation. Each system of law can be seenas a tool designed, within a particular climatic setting, to manage the dynamiccompeting efforts of individuals to control some part of the water resource. Theriparian doctrine was the foundation of water laws in the water-abundant easternstates while prior appropriation developed in the more arid western section ofthe continental United States. While state water laws have changed significantlythrough the decades, the fundamental principles of the riparian doctrine and priorappropriation continue to shape the basic character of state water laws. Table Ipresents a brief synopsis of the nature of water rights under these two systems oflaw as well as under the newer riparian- based permit systems now widely used inthe eastern states. The permit systems are described below.

Under the riparian doctrine, the owner of land adjacent to a water source has theright to make ‘reasonable use’ of the water on the riparian land. The riparian systemwas essentially court-made property law based on the common law of England.In both England and the eastern United States a humid environment and abundantsurface water led to few conflicts over exclusive (e.g., consumptive) uses of water.In fact, the possibility of exclusive use was ignored in early statements of riparianprinciples that guaranteed riparians enjoyment of the full unaltered natural flow ofa stream. Rather, riparian water law was designed to address conflicts that revolvedaround potentially competing instream uses of water, such as for the operation ofmills (Rose, 1990).

Under the prior appropriation system, the party with the oldest right has firstpriority to the available water. Junior users may not exercise their rights until allolder rights have been satisfied. This system makes it relatively clear who has theright to make use of each unit of water as flow levels fluctuate due to drought,seasonal variability, or sporadic storm flows (Chandler, 1913; Hutchins, 1971;Beck, 1990).

The prior appropriation system emphasized the private property nature of theright to use water that had been physically possessed and, in the process, succeed-ed in effectively privatizing much of the water in the western states. In contrast tothe eastern states, where non-consumptive instream uses of water were historical-ly important, early economic uses of western surface waters were predominantlyout-of- stream and consumptive in nature. Because prior appropriation laws weredesigned to promote ‘productive’ water uses, most made no provision for estab-lishment of water rights for instream uses other than for hydropower. Only very


Table ICharacteristics of U.S. Water Rights1

Prior Riparian Riparian-basedappropriation permit

Limits of right Specific place of Unquantified, Specificdiversion, quantity/rate ‘reasonable use’ quantity/rate ofof diversion, place and relative to uses of diversion; place andtype of use other riparians type of use

Basis of Physical control, Ownership of land Use, as defined byentitlement continued ‘beneficial’ adjacent to water permit

use source

Duration of Permanent, except for Permanent, but subject Temporary, durationright abandonment or to change with the of permit

forfeiture due to changing uses of established at timecontinued non-use other riparians of issuance

Allocation rule First in time, first in Similarly situated Priority establishedright riparians share co- by code; within

equal rights classes by stateagency discretion

Enforcement of State engineer or Civil court in response State waterallocations equivalent; court to suits resources

department; court

Transferability Yes, subject to No Rules vary, inrequirement of no practice few or nodamage to other vested transferswater rights

1 Tarlock (1989).

recently have western states revised their water laws to allow establishment ofinstream water rights for environmental, aesthetic and recreational purposes (Mac-Donnell and Rice, 1993). In most cases, only a public agency may hold such rights.In practice, with limited budgets to purchase senior rights, most instream rightshave such junior status that they may be of little practical significance (Wilkin-son, 1989). In some cases, however, states allow private groups to purchase senioragricultural water rights and donate them to instream use in perpetuity (Colby,1993).

2.2. ADAPTATIONS TO CHANGING VALUES AND DEMANDS

In the western states, rapid population influx and urbanization have created newdemands for water in areas where farmers and ranchers long ago appropriatedthe reliable supplies. Increasing environmental concerns and the elimination of


federal subsidies for new water projects have simultaneously reduced the optionsfor developing new sources of supply. While certainty of supply remains a dominantconcern to water users in the western states, flexibility to move water from onetype of use to another has become increasingly valuable. The value of flexibility isreflected in increasing numbers of market transfers of water rights throughout theregion and in efforts to devise new mechanisms to facilitate short-term transfers ofwater entitlements.

Under the prior appropriation system, transfers of water from one place or typeof use to another may not result in damage to any other valid water right (MacDon-nell, 1990a). Where there is no buffer of unappropriated water, any transfer couldpotentially impose such damages by altering the quantity, location, timing or qual-ity of return flows. Transfer proposals thus often generate significant transactioncosts (MacDonnell, 1990b) in the form of legal fees, costs of hydrologic analyses,and time and effort devoted by all parties whose rights could be affected as eachseeks to ensure a favorable definition of the transferable limits of the right.

As transfer proposals have become more frequent, two opposing trends havebecome evident. On the one hand, parties interested in facilitating transfers havesought to clarify the legal definition of a transferable right (Anderson, 1983) and toimprove documentation of existing rights through the adjudication process. Othershave increasingly called for the protection of community values derived from thecontinuance of historical agricultural uses (Ingram and Oggins, 1990; NRC, 1992).

The value of recreational and environmental uses of water has also increased. Tosome extent, these values are also being expressed in water markets (Colby, 1993).However, since water laws in most states do not provide for private ownership ofinstream water rights and since environmental, aesthetic and recreational uses tendto be non-exclusive, the role of market transfers has been limited.

Instead, the expression of environmental and recreational water demands hasoften taken the form of efforts to change the rules of the game by which water isallocated, either through legislation or through court challenges of other proposedor ongoing water uses. With respect to legislation, environmental interests haveactively supported improved transferability of water rights, because they see markettransfers as an environmentally less damaging alternative to new dams. On theother hand, they have also sought to reallocate water to environmental purposes byfavoring redefinition of water rights that are currently contributing to environmentaldamage, either through the courts (e.g., National Audubon Society v. Superior Courtof Alpine County, 658 P.2d 709) or through legislation such as the 1992 CentralValley Project (CVP) Improvement Act (Title XXXIV of Public Law 102-575)which mandates the allocation of 800,000 acre-feet of Central Valley Project watersupplies to implement fish and wildlife restoration.

As interest in the preservation and restoration of aquatic environments hasgrown, an increasing number of individuals have questioned the legitimacy of theprior appropriation system. Thus, the growth in demand for ‘common property’aspects of western streams has led to growing pressure for more of a ‘public trust’


approach to western water law, entailing greater limits on the exercise of privaterights and increased administrative control over water uses that pose a danger toinstream values (Wilkinson, 1989; Butler, 1990).

In the eastern states, population growth and expanding municipal water with-drawals have made specific claims to a part of the water supply a more prominentconcern than had been the case in the nineteenth century. As municipal and otherout-of-stream water demands have increased, the weaknesses of the reasonableuse rule in allocating water among rival consumptive uses has led to increasingpressures to clarify and quantify entitlements. In response to actual or anticipateddifficulties in the delineation and enforcement of competing riparian rights, themajority of the traditional riparian states have modified their water laws. Sever-al states have adopted permit systems while others have adopted only registra-tion requirements or regulations governing particular types of uses (Sherk, 1990;Abrams, 1990). The permit systems typically establish threshold use amounts, thusexempting small diversions from all or part of the permit requirements. Whererequired, permits are generally fixed- duration, non-transferable licenses to divert aspecified quantity of water. Permitting agencies maintain administrative oversightof permitted uses and do not convey permanent property rights to permit holders.

This attention to clarifying rights to withdraw water from eastern streams hasnot supplanted concern for preserving streamflows, but the players have changed.A growing cadre of conservationists and recreational users, seeking to protect andrestore the quality of stream environments, have replaced mill owners as the primarychampions of instream flows. Thus, it appears that in both the eastern and westernstates, inherently joint, instream uses are currently increasing in importance. If thistrend continues, planning for the impacts of climate change and adaptation to thoseimpacts as they actually unfold will likely occur in the context of ongoing efforts toclarify and redefine the rights of consumptive water users as against other partieswho value the maintenance of instream flows primarily for ecological, aestheticand recreational purposes. Since these latter values are likely to be sponsored bypublic agencies, ongoing struggles to redefine the boundaries between private andpublic discretion over water resources are likely to be part of the institutional settingwithin which the effects of climate change will be addressed.

2.3. OTHER INSTITUTIONAL CONSIDERATIONS

The prior appropriation and riparian/permit systems of water law constitute theinstitutional foundation for water use decisions in the United States. The fullinstitutional infrastructure also includes many other laws, programs, contracts andadministrative arrangements. In some western river basins, where federal waterstorage projects control a large portion of the annual streamflow, the contracts andoperating rules pertaining to the projects are the dominant institutional arrange-ments. Congress authorized these projects to promote rapid development of thewestern states, always building subsidies to irrigated agriculture into the repay-


ment contracts (Wahl, 1989; Wilkinson, 1989). Projects were thus prizes, eagerlysought by western development interests.

In some instances, the promise of federal water projects served as the impetusfor interstate agreements on the allocation of rivers crossing state boundaries.In the case of the Colorado River, California’s desire to secure congressionalauthorization of the All American Canal and Boulder Canyon (Hoover) Dampropelled negotiations for the 1922 Colorado River Compact. The Compact dividedthe water between the Upper and Lower Basins, obligating the Upper Basin todeliver a moving ten-year average of 7.5 maf (million acre-feet) per year at LeeFerry. Except for Upper Basin water rights that were perfected prior to the Compact,this gives the Lower Basin priority in the event of reduced flows (MacDonnell etal., 1995). In addition, the Lower Basin has the larger right because Compactallocations were based on an assumed average flow considerably larger than thelong-run average of 13.5 maf suggested by tree-ring evidence (Stockton and Jacoby,1976). Later, the Upper Colorado River Basin Compact clarified how the burdenof meeting the obligation to the Lower Basin would be divided among the UpperBasin states, clearing the way for federal support for major storage projects inthe Upper Basin. The system of reservoirs now in place in the Colorado Basin iscapable of storing approximately four times the average annual flow of the River.

The Compact, subsequent statutes, an international treaty, court decisions andproject operating rules together comprise the ‘Law of the River’. A recent study ofthe potential impacts of a severe sustained drought found that this set of institutionswould leave sensitive biological resources, hydropower generation and Upper Basinwater users vulnerable to damages despite the extraordinary engineering attemptsto drought-proof the River. The study team also found that certain proposed insti-tutional changes could considerably alter the level and incidence of the damages(Booker, 1995; Kenney, 1995; Lord et al., 1995; Sangoyomi and Harding, 1995).

The past quarter century has witnessed tremendous change in federal involve-ment in the development of new water projects, operation of existing federalprojects, management of water quality, and protection of aquatic environments.The so-called ‘iron triangle’ between local water development interests, the federalconstruction agencies, and congressional public works committees that fostereddecades of pork-barrel water projects has given way to a newer pattern of greatlyreduced federal funding for water projects, greater cost sharing by project bene-ficiaries and changes in the types of projects receiving federal support (Cortnerand Auburg, 1988). Coalitions of environmentalists and congressional cost- cuttersbegan to force changes in the established system of project authorization in thelate 1960s and early 1970s (Ingram, 1972). The Reagan Administration furthercurtailed federal involvement in water resources planning by eliminating the WaterResources Council, the joint federal-state river basin commissions and federalgrants for state planning, and by significantly cutting federal funding for waterresources research. “By 1982, most of the institution framework for federal waterresources policy had been dismantled” (Cortner and Auburg, 1988, p. 1052).


While federal financing of water projects has greatly diminished, federal reg-ulation of water use and development has become an increasingly important partof the set of institutions governing the nation’s water resources. Federal influ-ences include federal jurisdiction over navigable waters, federal laws (e.g., CleanWater Act [P.L. 92-500, 1972]; Safe Drinking Water Act [P.L. 93-523, 1974]), andSupreme Court cases (e.g., Sporhase v. Nebraska ex rel. Douglas, 458 U.S. 941, 102 S.Ct. 3456, 1982; City of El Paso v. Reynolds, 365 F. Supp. 379 [D.N.M. 1983],1983) (Wilhite and Rhodes, 1994). International treaties and interstate compactsmay also constrain water allocation decisions at the state level, if the limits imposedby such agreements are binding and enforced (Bennett, 1994).

Two examples of federal control that may become increasingly important ifwater availability diminishes are the Endangered Species Act (P.L. 93-205) andreserved water rights for federal and Native American lands. The EndangeredSpecies Act, which in recent years has become a forceful instrument for the pro-tection of aquatic and other water-dependent biota, may restrict future use anddevelopment of water supplies (OTA, 1993). In addition, the Supreme Court hasheld that when the federal government established Native American reservations,National Parks and other permanent federal land reservations, it also implicitlyreserved sufficient water to serve the purposes of the reservation (Tarlock, 1989).The date on which the reservation was established determines the seniority of thesereserved water rights, giving them priority over most appropriative water rights.In many cases, Native American claims have not yet been quantified or exercised,and controversy has accompanied the exercise of federal reserved water rights forpurposes of environmental protection (OTA, 1993). Both federal reserved rightsand Native American rights have the potential for leading to future conflicts withother water users, particularly if streamflows diminish.

Despite the importance of federal influences, most of the ongoing authorityover the use and management of water resources rests at the level of the state,the local supplier and the individual irrigator. Administrative arrangements differsignificantly, and contracts, bylaws and authorizing legislation often constrain thepricing, allocation and water trading options available to irrigation districts, otherlocal suppliers and their members.

In most states, a state engineer’s office or its equivalent handles the issuanceof new water rights or water use permits, approval of transfers and enforcementof existing rights. The powers granted to these offices, their budgets, establishedprocedures, and the quality of the records available to them differ considerablyfrom one state to the next. In eastern riparian states that have not yet adoptedpermit systems, the resolution of any disputes is handled by the courts. In the west,Colorado uses a unique system of specialized water courts for the establishmentand transfer of water rights, coupled with active ongoing enforcement by statedivision engineers. Such differences have a significant impact on the transactioncosts incurred in transferring water rights and therefore on the nature and amountof water transfer activity (MacDonnell, 1990b). The fact that water transfers are


more difficult in some jurisdictions than in others suggests that such state-leveladministrative arrangements will have an important bearing on the costs of adaptingto the effects of climate change.

3. Challenges Arising From Prospective Climate Change

How might climate change affect the rights of competing users to the multiplefacets of a water resource? What institutional factors will make it easy or difficultto adapt to climate change within the context of each system?

The physical effects of trace gas-induced climate change on streamflows willdepend on changes in temperatures, evapotranspiration and precipitation. Smallersnowpacks may lead to reduced summer streamflows in some river basins. A studyof the Sacramento Basin estimated, for example, that if temperatures increased by2 �C and precipitation patterns remained unchanged, summer streamflows (June–Aug.) would decline by 22 percent while winter runoff (Dec.–Feb.) would increaseby 8 percent (Gleick, 1987). Similar results were obtained in a study of the AnimasRiver Basin in Colorado, which estimated that a 2 �C warming would reducesummer streamflows (July–Sept.) by roughly 40 percent (Schaake, 1990). In basinsin which there are few acceptable options for additional artificial storage, suchchanges in the hydrologic regime imply a significant reduction in water availabilityto service competing demands. Those estimates are based only on changes intemperatures.

Analyses of climate change scenarios for river basins in the eastern states alsosuggest the possibility of reduced summer streamflows as well as increased winterrunoff in those areas where there are currently winter snowpacks. A study of theDelaware River Basin (McCabe and Ayers, 1989) estimated that large percentageincreases in precipitation would be required to maintain summer soil moisture, andthat annual runoff would decline by 9–14 percent with a 2 �C warming and 20–25percent with a 4 �C warming without offsetting increases in precipitation.

Surface runoff is sensitive to changes in temperatures and precipitation, andchanges in interconnected aquifers will further affect streamflows (White, 1985).For example, if warmer temperatures cause soil moisture depletion, infiltration toaquifers will diminish. As the level of an aquifer declines, groundwater dischargeto surface streams will decline and seepage losses from surface water bodies tothe aquifer may increase. Changes in precipitation may offset or exacerbate thehydrologic changes that are predicted on the basis of temperature changes alone –and the climate models are a long way from being able to accurately forecast howregional precipitation regimes may change in a warmer world (Tegart et al., 1990;Waggoner, 1990).

The prospect of climate change thus creates considerable uncertainty regardingfuture water availability. What problems might arise from that uncertainty itselfand how might the problems differ as a result of the initial legal framework and


existing patterns of use and availability? In the west, reliable hydrologic informa-tion is particularly valuable for assessment of the impacts of proposals to transferor alter the use of a water right. Reliable estimates of the statistical distributionof streamflows, consumptive use and evaporative losses from natural channels andconveyance facilities are important to state engineers responsible for determiningthe availability of unappropriated water. They are equally important to parties seek-ing to establish new water rights and to those interested in ensuring the preservationof aquatic environments.

Climate change will affect not only initial surface runoff into a stream system,but also rates of evaporative loss, seepage to groundwater aquifers, recharge fromthose aquifers and rates of consumptive use from irrigation withdrawals alongthe entire stream system. Because the ultimate direction and magnitude of thosechanges may remain unpredictable until climate change is well under way, estimatesof the reliability of new public or private rights and of the impacts of water righttransfers will be both fraught with uncertainty and increasingly open to dispute.In the case of transfer proposals, water authorities often limit the quantity ofwater transferred from an existing user to another place or type of use to theseller’s historic consumptive use to prevent impairment of other water rights. Forexample, half of the water diverted to an irrigated field might currently be lost toevapotranspiration while the remainder returns to a usable water body. If that rightis transferred, the buyer’s diversion right would be established to allow expectedconsumption equal to half of the original diversion right. In addition, the watercourt or state authority may impose terms and conditions on the transfer to furtherprotect other water users against changes in the timing or location of return flows.

The prospect of climate change makes it more difficult to forecast both futureconsumptive uses and the future availability of water to keep existing uses intact.For example, warmer temperatures could cause return flows from a new use to besmaller than anticipated by increasing evaporative and seepage losses.

Even under the presumption of a stable climate, imprecise hydrologic informa-tion is now frequently at the heart of costly conflicts over proposed water transfersand new water developments. This suggests that uncertain changes in the climaticregime will likely enhance the basis for such disputes. Policymakers, hydrologists,administrators and the judiciary should therefore give careful attention to the ques-tion of how such climatic uncertainties might enter into decisions regarding thedevelopment or transfer of water rights and to the issue of who will bear the riskof mistaken assessments.

In the eastern states, voluntary transfers of established water rights have notyet become an issue, but the courts and water authorities are concerned with thepotential impacts of new uses on other parties. Forecasting those impacts in thepresence of potential climate change is likely to be difficult, particularly in stateslacking reliable information on water uses. Unlike the western states where waterrights, once granted, tend to be viewed as permanent property rights, rights heldunder permits in most of the eastern states are explicitly of limited duration. This


might suggest that decisions based on hydrologic assumptions that later proveinaccurate would be easier to ‘fix’ than under the prior appropriation system’spresumption of relatively permanent rights. Eastern-state parties that have madesubstantial water-related investments, however, may be no more likely to quietlyacquiesce to reduction of their permit rights than would be western appropriatorsfaced with an administrator’s demand, grounded on the public trust principle, thatthey line their ditches or reduce their withdrawals to mitigate streamflow reductionscaused by climate change.

The uncertain hydrologic impacts of climate change may also complicate theenforcement of water rights even in the absence of proposed changes in water uses.The generally poor integration of groundwater and surface water rights in bothwestern and eastern states may present increasing problems if climate change altersthe entire hydrologic regime within interconnected groundwater and surface watersystems. Here, measurability is important. Where hydrologic models are available,they may be unreliable under conditions departing significantly from those on whichthe models were based, and there are many watersheds and aquifers for which thehydrology is poorly understood even for the existing climate. In addition, recordsof actual withdrawals, consumption and instream uses are frequently lacking evenin states that nominally follow the prior appropriation doctrine or that have adoptedpermit systems. Uncertainty about basic hydrologic relationships and inadequatewater use records could make it difficult to determine responsibility for changesin water availability under climate change (i.e., is the lower water table the faultof nature or your neighbor?) Such measurement problems may lead to disputes aswater authorities and users attempt to determine a fair and efficient allocation ofaltered supplies.

Now consider the case in which climate change is under way and water isbecoming more scarce. Because interannual variability will continue as the cli-mate system changes, it may take a very long time to clearly recognize any suchtrend (Rogers, 1994). Transitions to drier regimes are most likely to occur as agradual increase in the frequency of dry years, interspersed with wet periods, andgradual shifts in the timing of runoff and in the recharge/discharge interactions ofgroundwater and surface water systems.

Under the prior appropriation system, the impacts of increasing water scarcitywould fall most heavily on the most junior water users, as well as on environmentalvalues that have not been protected by the dedication of reliable senior rights toinstream flows. Junior users would have incentives to find ways to adapt, bothto individual dry periods and to mounting evidence of a shift to a drier regime.For example, they could make arrangements to buy or periodically rent moresenior water rights; they could invest in storage infrastructure, engage in waterconservation, develop programs for conjunctive use of groundwater and surfacewater; or they could decide to cease their water-using activities. Another option,of course, would be to lobby for the mandatory reduction and reallocation ofthe rights of their senior neighbors. Well-functioning water markets would tend to


reduce such pressures and, in the absence of mandatory reallocation, the differentialimpacts of a climate change on junior and senior water users would create furtheropportunities for the development of water markets.

Water markets are likely to be most effective where the water uses are primarilyexclusive or consumptive in nature, or if non-consumptive, involve a relativelysmall number of parties. Because most water uses are not fully consumptive,water markets will function efficiently only if the law protects third parties againstchanges in return flows. Trelease (1977) notes that providing that protection can becostly and time-consuming where rights are defined on the basis of diversion ratherthan on the basis of consumptive use. Consumptive use determines the availabilityof water to downstream parties, and it is typically difficult to measure. Recall thatclimate change may alter the relationship between diversions and consumptive useby changing conveyance losses and evapotranspiration from irrigated fields.

Privately arranged market transfers of water rights are unlikely to adequatelyprotect environmental values accruing to a large and amorphous public againstthe impacts of a shift to warmer and drier conditions. This is due to the fact thatvoluntary collective action to provide such public goods is limited by the incentiveof each individual to free-ride on the contributions of others. Government provisionof environmental goods may be more efficient than private contracting in such cases(Barzel, 1989; Eggertsson, 1990). The experience of the western states suggeststhat some form of action by state authorities will be required to provide appropriatelevels of protection for water quality and instream flows if drier conditions becomemore prevalent.

The Colorado River Severe Sustained Drought study provides analogical evi-dence that non-consumptive water uses would be more vulnerable to damagethan traditional consumptive uses. That study concluded that damages to non-consumptive uses could not easily be mitigated without changes in statutes orjudicial interpretations to give greater voice to those interests (Lord et al., 1995).

In the eastern states, the more fluid definitions of individual water rights mightdiscourage advanced planning on the part of private parties. Users might attempt,instead, to convince water authorities or the courts that their own uses are morereasonable and beneficial than those of competing users and therefore warrant betterprotection. Whereas multilateral negotiations and exchanges appear likely in thewest, the centralization of decision-making authority in the eastern permit-systemstates suggests that water users may concentrate on influencing the authorities. Theflexibility inherent in the permit systems thus can give rise to transaction costs inthe form of the efforts of competing users to plead their claims to a dwindlingresource. On the other hand, that very flexibility may make it easier to protectwater quality and instream uses than would be the case in the western states,where it may prove difficult to dislodge expectations that a water right entailsprotection of a particular rate of diversion and method of application regardless ofthe environmental consequences.


4. Recommendations

Both water allocation systems have potential strengths and weaknesses in the con-text of facilitating adaptation to climate change. The challenge is to determine themost effective way to enhance adaptive capacity in each institutional setting. Withinboth systems, water laws have accommodated considerable change in the level andnature of human demands on water resources. As individual states have experiencedchanging demands they have consciously or unconsciously made tradeoffs betweenthe up-front costs of modifying water statutes or administrative procedures to clar-ify the dimensions of individual water rights and the subsequent dispute- relatedtransaction costs arising from the efforts of water users to modify or expand theirwater uses. This investment problem is a continuing phenomenon that separatejurisdictions have handled differently. For example, some states have made greaterefforts to document existing water uses than have others.

The prospect of climate changes makes it more important to give explicit atten-tion to the tradeoff between the initial costs of clarifying the rights of multiple waterusers and the future costs of conflicts that may arise if water availability changes.The desires of competing water users for certainty, flexibility and protection ofenvironmental values must now be accommodated within the context of increasinghydrologic uncertainty. This suggests a number of factors that policymakers shouldconsider in the upcoming decades as water statutes are modified, as adjudicationsare carried out, and as decisions are made regarding water transfers, issuance ofnew permits and protection of environmental values.

A. Improve the Predictability of the Limits of Individual Rights under a Variety ofPossible Climatic Conditions:While the prior appropriation system clearly defines the relationship betweenstreamflows and diversion rights, other dimensions of a right such as allowableconsumptive use can vary, to the detriment of other users, as climatic conditionschange. This is due to the fact that the relationship between the quantity of waterdiverted and consumptive use of that water is not constant. Under warmer con-ditions, a larger fraction of the water is likely to be lost to evaporation fromconveyance channels and to crop evapotranspiration, thus reducing return flows. Itmay be valuable to define limits on allowable consumptive use as a basis for reduc-ing the adverse impacts of climate change on junior users and instream flows. Forexample, state regulations could specify consumptive use thresholds at which own-ers of existing water rights could reasonably be required to modify their diversionsand application practices as climatic conditions change. State water authoritiesshould explicitly incorporate such conditions in the specification of any new waterrights.

Under the permit systems in eastern states, water authorities could provide betterpredictability by clarifying how they are likely to reduce the right when streamflowsdecline. They could lay out conditions at the time of initial permit issuance and


update them according to published rules at each permit-renewal interval. Suchimprovements in the definition and predictability of water rights would enhancetransferability by providing better security to purchasers and potentially affectedthird parties.

B. Further Document and Clarify Consumptive Use Rights:The prospect of climate change suggests that it may be valuable to better documentwater withdrawals and consumptive uses, as well as natural variations in stream-flows and groundwater levels. Such efforts should be targeted at reducing the basisfor future disputes and providing adequate information for water transfers shouldwater scarcity become more prevalent. In pursuit of this objective, water authori-ties should attempt to balance the likely value of additional information against thepotential costs of ‘information overload’. Parsimony in data reporting requirementsand the design of efficient systems for the storage and timely retrieval of relevantinformation should be guiding principles. The benefits of improved documentationare likely to accrue both to parties who currently withdraw water for exclusiveuses and to the broad public interested in preserving environmental, aesthetic andrecreational values associated with water resources. This suggests that the costs ofimproved documentation should be borne by both current water users and generaltaxpayers. The appropriate level of investment and distribution of the cost burdenare inherently public decisions.

C. Better Integrate Groundwater and Surface Water Rights:Possible changes in the hydrologic interactions between groundwater and surfacewater systems may reinforce the value of clarifying the rules for enforcement ofrights within such interconnected systems. There is an inherent lag between changesin groundwater extractions and resulting changes in streamflows. This makes short-term administration of withdrawals an ineffective method of enforcing the rightsof downstream surface water users against parties pumping water from a tributaryaquifer. More effective options for offsetting the impacts of groundwater pumpingare available (MacDonnell, 1988) and their application may become increasinglynecessary to ensure a fair balancing of the rights of users of surface water andgroundwater. In planning for the integration of groundwater and surface waterrights, water authorities should give attention to how the hydrologic interactionsbetween groundwater and surface water sources may be affected by a range ofpossible future changes in the local and regional climate.

D. Plan for Adaptation:State and local planning would reduce the likelihood of implementing programsthat are later revealed to be unnecessary or inordinately controversial. Responsescould be phased in as the actual hydrologic effects of climate change becomemore evident. It would be valuable to begin planning both for the management ofincreased flood risks and for water allocation in the event of increased scarcity, in


each case identifying policies to be pursued if conditions become wetter or drier.In addition, policymakers should attempt to assign planning, data collection andadministrative responsibilities to make most effective use of evolving informationabout water supply conditions and water-use values.

It may also be valuable to re-establish interstate or national-level forums forwater resources planning. Interstate river basin commissions could facilitate thedevelopment of flexible options for responding to the uncertain impacts of climatechange. The report of the Office of Technology Assessment (OTA, 1993) discussesthe advantages of comprehensive water resource planning and management at thebasin level. For example, basin-wide coordination may allow multiple demandsto be met more efficiently than would be possible with uncoordinated reservoirmanagement. The value of such coordination may increase if there are significantchanges in water availability or streamflow variability. In addition, as the scope ofplanning and coordination are expanded, a wider range of options for respondingto changing water supplies and demands is likely to be available.

At the national level, Congress could reactivate the National Water Council orcreate a similar high-level coordinating body. The OTA report argues that such abody “: : : could play an important role in improving cooperation and coordinationamong the many Federal agencies with water- related responsibilities and amongFederal State, and local governments and the private sector” (OTA, 1993, p. 249).It could also serve as a clearing house for research and data relating to changinghydrologic conditions.

E. Create Flexibility to Move Water to More Valuable Uses:Flexibility in water allocation can be achieved either through markets or throughadministrative action. The key is to ensure that the method chosen provides afair and efficient means of moving some aspect of the water resource to a morevaluable use. Unproductive disputes, efforts devoted to lobbying for bigger sharesof the resource and excessive search costs must be avoided, because these tend towaste the potential gains from reallocation of the resource. Among the importantconsiderations in determining the appropriate locus for decision making are accessto information and incentives to act upon that information. For water uses thatare primarily exclusive in nature, Trelease (1977, p. 82) argues that water usersthemselves have the best information about the value of the water, and their self-interest will channel the resource from low valued uses to more highly valued usesif water becomes scarcer relative to their demands.

The bureaucrat trying to decide the best use of water as between agricultureand industry will have to investigate, hold hearings, hire experts, financea university study and make findings. The manager of the Tootsie TextileCompany and Farmer Jones, sitting at the bargaining table, can tell the answerin a minute by a glance at the bottom line of last year’s books.


This argues that voluntary reallocation should play an important role in determiningthe future distribution of scarce water among competing uses. As noted previous-ly, this method of allocation may be less effective where non-exclusive uses areinvolved, but public agencies could represent such interests in a market settingif they are provided with budgets to buy or rent water rights for environmentalpurposes.

The effectiveness of water marketing in promoting flexible adaptation to pro-spective climate change will depend on the nature of the markets. At present, theprocess for approving water transfers in the western states involves considerabletransaction costs (MacDonnell, 1990b). As a result, most transfers between differenttypes of uses tend to be permanent transfers of large blocks of water. Such largetransfers are not a particularly effective tool for responding to the effects of climaticvariability or to the uncertain prospect of climate change. Rather, policymakersshould focus greater attention on promoting shifts of small quantities of water andtemporary transfers from senior to junior users during periods of low flows. Thiscould be accomplished by streamlining administrative procedures for temporarytransfers or by establishing formal water banks. California used such banks in 1991,1992 and 1994 to mitigate the uneven impacts of a persistent drought. Althoughthere have been only a few other examples of functioning water banks to date,experience suggests that rules and procedures can be designed to allow timelytransfers of water from lower to higher valued uses while effectively managingthe possible environmental and third party impacts of the altered pattern of use(MacDonnell et al., 1994).

Similar mechanisms could be established as needed in the eastern states, butto function effectively, the quantitative limits of the entitlements would have to beclearly established for the period to be covered by the bank. For example, a waterauthority could announce firm cut-backs of permit rights during a drought butallow permit holders to sell part of their entitlements or purchase additional waterthrough the bank. Temporary and partial transfers as through a water bank couldallow water users to improve upon the distribution of entitlements established bythe permitting agency and could ease the burden of adjusting to any reductions inpermit rights instituted in response to the effects of climate change.

F. Enhance the Ability to Condition Rights in a Fair and Efficient Manner toProvide Appropriate Protection for Environmental Values:Given established patterns of water use and established expectations, efforts tomitigate the degradation of streams, lakes and wetlands that may result from climatechange will raise difficult questions of equity and efficiency. Careful attention tothe proper roles of market allocation and administratively imposed limits on theexercise of individual water rights will be important to ensure efficient protectionof the public trust, but there is also an inherent distributional question. That is: whoshould bear the cost of environmental preservation and restoration when climatechange is a factor in the degradation?


Should the water users bear the full cost of preserving environmental values inthe presence of such a change or should their liability be limited to not increasingtheir own consumptive use in response to warmer temperatures, reduced precip-itation and higher rates of evapotranspiration? Provided with adequate budgets,public agencies might be able to preserve streamflows and water quality by buyingwater from existing users, but that option assumes that the public at large shouldbear the entire burden of preserving public trust values in the presence of climatechange.

Advanced consideration of the distribution of rights and responsibilities in theevent of significant change in the hydrologic regime could help to avoid costlyfuture disputes. Open discussion of the criteria by which policy options should beevaluated will also be valuable. Authorities could specifically condition new waterrights to alert users to possible future modification of the rights and to explicitlyspell out the climatic and environmental conditions under which such modificationscan be expected. In addition, it would be valuable to develop clear policy statementsregarding modifications of established rights in the event of future climate changeor long-run drought, together with explicitly stated standards of evidence that willbe used to determine when hydrologic conditions have changed sufficiently towarrant implementation of the regulations.

G. Create and Preserve a Water Supply ‘Safety Margin’:Where no buffer of unappropriated water exists, it is inevitable that some waterusers will be made worse off if conditions become drier. Even where streamflowsare not so fully allocated that junior out-of-stream users face a significant risk ofbeing unable to exercise their rights, public instream values may suffer under drierconditions. The possibility of conflicts between competing water users might bereduced if instream flows are explicitly treated as a buffer to be used to absorb theimpact of changing climatic conditions. Rather than setting a single minimum flowstandard to be used as a target for avoiding serious adverse impacts on fisheries andother aquatic resources, a range of environmentally desirable flow levels could bedefined. The lower level might serve as a trigger for water authorities to enhanceinstream flows by purchasing water or implementing restrictions on existing rights,while the upper level would be used as the target for conditioning new rights. Forexample, administrators could grant new permits subject to the condition that theynot deplete streamflows beyond the upper flow- level target. If flows increase, waterusers could fully exercise the new rights. If flows decline, the impact would fall firston the conditioned permits, then on the buffer and finally on current water uses.Where water is already fully appropriated, authorities could create such a bufferby purchasing water rights from willing sellers to reduce existing consumptiveuses. Where unappropriated water is available, they could more easily create sucha buffer by incorporating appropriate conditions in the definition of new rights andby closing some streams to new appropriations unless and until there is considerableevidence that wetter conditions are likely to prevail.


5. Conclusion

The time has come for innovative thinking on the question of how our waterallocation institutions should function to improve our capacity to adapt to theuncertain but potentially large impacts of global climate change on regional watersupplies. Given the climatic uncertainties and the very different institutional settingsthat have developed in this country, there is no simple prescription for adaptation.

We have identified several elements that decisionmakers should keep in mindfor the design of more adaptive water institutions. By pursuing these goals as waterlaws and administrative procedures are updated, it should be possible to reduce thedisruption, potential for disputes and resource degradation that might otherwiseresult if climate change significantly alters regional hydrologic regimes.

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